Extraction of condensed ring, polycyclic aromatics from wax



United States Patent fifice 3,058,965 Patented Oct. 16, 1962 3,058,905 EXTRACTION F CONDENSED RING, POLY- CYCLIC AROMATICS FROM WAX Thomas A. Washall, Claymont, Del., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Filed June 17, 1960, Ser. No. 36,737 12 Claims. (Cl. 20824) This invention relates to the extraction of condensed 4- and S-ring aromatic hydrocarbons from hydrocarbon wax fractions and, more particularly, it relates to a process for extracting condensed 4- and S-ring aromatic hydrocarbons from hydrocarbon wax fractions utilizing dimethyl formamide as the selective solvent.

The use of hydrocarbon waxes as coating agents for materials utilized to package foods has increased rapidly in recent years. These hydrocarbon waxes are derived largely from petroleum sources and this use has presented the petroleum refiner with numerous problems. In addition to producing Waxes which have the desired tensile strength, adhesivity, flexibility, moisture-proofness and similar properties, it is also necessary that such waxes have a desirable color, be free of odor and free of deleterious compounds. For example, it has been found that certain aromatic compounds are deleterious and, in particular, the condensed 4- and S-ring aromatic compounds are undesirable. Small quantities, however, of diand tri-cyclic condensed ring aromatics having long alkyl side chains have been found useful in certain wax fractions such as the microcrystalline waxes, since these compounds impart certain desired physical properties to the wax, such as adhesivity, low temperature flexibility and the like. It, therefore, has become a problem for the refiner to remove the undesired condensed 4- and S-ring aromatic hydrocarbons from wax fractions while retaining the small amounts of desired aromatics in the wax. This problem is particularly difficult since the condensed 4- and S-ring aromatic hydrocarbons are present in very small amounts.

A method now has been found for selectively extracting the condensed 4- and S-ring aromatic hydrocarbons, although such hydrocarbons may be present in small amounts, from hydrocarbon wax fractions by the use of a dimethyl formamide solvent.

It is an object, therefore, of this invention to provide a process for the selective extraction of condensed 4- and S-ring aromatic hydrocarbons from hydrocarbon wax fractions.

It is another object of this invention to provide a process for extracting condensed 4- and S-ring aromatic hydrocarbons utilizing dimethyl formamide as the solvent.

Other objects of this invention will be apparent from the detailed description thereof and the claims that follow.

In accordance with this invention a hydrocarbon wax fraction containing a condensed 4- or S-ring aromatic hydrocarbon or mixtures of sych hydrocarbons is contacted with the dimethyl formamide solvent at a temperature ranging from 5 F. to about 60 F. above the melting point of the hydrocarbon wax fraction. After thoroughly mixing the solvent and wax, the mixing is discontinued and the mixture, while at the temperature of mixing, is allowed to separate into two phases, one phase being rich in wax hydrocarbons substantially free of the condensed 4- and S-ring aromatic hydrocarbons and the other phase comprising the solvent containing the extracted condensed 4- and S-ring aromatic hydrocarbons together with small amounts of other hydrocarbons. In general, the solvent is removed from the hydrocarbon wax by distillation, i.e., vacuum stripping and, if desired, the solvent may be recovered from the solvent phase by conventional distillation.

The condensed ring aromatic compounds which can be extracted by the process of this invention are exemplified by the following 4-ring hydrocarbons and S-ring hydro carbons, the trivial name, if any, appearing first and the descriptive name of the same compound appearing in parentheses following the trivial name: aceanthrylene (cyclopent[de]-anthracene), acephenanthrylene (cyclopenta[jk]phenanthrene), fluoranthene (benz[a1acenaphthylene), naphthacene (2,3-benzanthracene), benzEalanthracene (1,2-benzanthracene), chrysene (1,2-benzophenanthrene), benzo[c]phenanthrene (3,4-benzophenanthrene), triphenylene also called isochrysene (9,10-benzophenanthrene), pyrene (benzo[def]phenanthrene), indenolf2,1 b]fiuorene, indeno[2,1 aJfiuorene, indeno [1,2-a1fluorene, indeno[2,l-c]fluorene, dicyc1opent[a,c] anthracene, -benz[k]acephenanthrylene (naphth[2,3-e] acenaphthylene), benz[e]acephenanthrylene, benzoide] cyclopentEa] anthracene, dibenzo[c,lm]fiuorene (benz[a] aceanthrylene), benz[e]aceanthrylene, benz[a]acephenanthrylene, benz[1]aceanthrylene (naph[l,2 d]acenaphthylene, benz[j]aceanthrylene (naphth[2,l-d]acenaphthylene, benzo[fg]cyclopent[a]anthracene, cyclopenta[hi] chrysene, naphtho[1,8,7,6-cdef]fiuorene, pentacene (benzo [b] naphtha cene) benzo [a] naphthacene, dibenzo[b,h]phenanthrene, benzo[b]chrysene (dibenzo [a,h]phenanthrene, dibenzo[b,g]phenanthrene, dibenz [a,c] anthracene, dibenz [a,j] anthracene, dibenz[a,h] anthracene, picene (dibenzo[a,i]phenanthrene), benzoEg] chrysene, benzo [c] chrysene, dibenzo [c,g] phenanthrene, benzo[a]pyrene, benzo[e]pyrene, perylene (dibenz[de,kl] anthracene).

In addition to the foregoing compounds, the low molecular weight alkylated derivatives of these condensed 4- and S-ring aromatic hydrocarbons may be extracted by the process of this invention. The low molecular weight alkyl substituents contain 6 or fewer carbon atoms and may be either paraffinic or cycloparafiinic in structure. The process of this invention is also applicable for the extraction of the partially saturated derivatives of the above-named compounds, i.e., derivatives wherein one or more carbon atoms of one of the rings is saturated.

The hydrocarbon wax fractions from which the described condensed ring aromatic hydrocarbons may be extracted according to the process of this invention include the so-called microcrystalline waxes produced by the solvent extraction and deoiling of heavy petroleum distillate or residuum stocks. These hydrocarbon microcrystalline waxes which are sometimes designated as amorphous or petrolatum waxes, may range in melting point from F. to 200 F. as measured by ASTM Method D-l27. They are further characterized by being relatively light in color ranging from one-half to two as measured by ASTM Method D and having an oil content not in excess of about 1.0 to about 1.5 percent as measured by ASTM Method D721. The extraction process of this invention is also applicable to the removal of the aforementioned condensed 4- and S-ring aromatic hydrocarbons from refined parafiin waxes and scale wax, in particular, refined parafiin wax fractions melting between 120 F. and F. Wax fractions containing large amounts of oil are to be avoided since the dimethyl formamide will then act as a deoiling solvent and its solvent power will be utilized for deoiling rather than for selectively extracting the aforementioned condensed 4- and S-ring aromatics from the wax.

Naturally-occurring hydrocarbon waxes similar to the petroleum hydrocarbon waxes, for example ceresins and similar hydrocarbon waxes, also may be extracted by the method of this invention in order to selectively remove the condensed 4- and S-ring aromatic hydrocarbons therefrom.

The solvent which is utilized for extracting the condensed 4- and S-ring aromatics from the hydrocarbon wax fractions in accordance with the process of this invention is N,N-dimethyl formamide which, for convenience, is referred to herein simply as dimethyl formamide. Although this solvent may be employed in admixture with modifiers such as water or alcohols, no advantages have been found for employing these modifiers. Moreover, since dimethyl formamide exhibits its greatest selectivity for the condensed ring aromatic when in the pure form, it is preferred to use the dimethyl formamide without modification.

The quantity of solvent utilized may range -from.an amount corresponding to 0.5 gram of dimethyl for-mamide per gram of wax to grams of dimethyl formamide per gram of wax. Although good results may be obtained by utilizing the dimethyl formamide in a single treat when batch treating, it is preferred to utilize two or more successive extractions in order to obtain the most efiicient removal of the condensed 4- and S-ring aromatic hydrocarbons. Thus, it has been found that three consecutive batch treatments on a particular wax sample with 0.5 gram of dimethyl formamide per gram of wax in each treat gives completely satisfactory results with respect to the extraction of the condensed 4- and S-ring aromatic hydrocarbons.

The extraction process of this invention is carried out by admixing the hydrocarbon wax at a temperature above its melting point with the dimethyl formamide. It is preferred to add to the melted wax dimethyl formarnide which has been heated to approximately the temperature of mixing. The temperature of mixing should range from about 5 F. to about 60 F. above the melting point of the hydrocarbon wax in order to give the most eflicient extraction of the condensed 4- and S-ring aromatics from the wax. The solvent is agitated with the melted wax for a sutficient time to give thorough contacting. This time will be dependent on the efiiciency of agitation, the viscosity of the wax, and similar factors, all of which influence the degree of contacting of the solvent with the wax. If a highly efficient agitator is employed so that the contacting is very thorough, mixing times as short as five minutes may be employed. However, since the quantites of condensed 4- =and S-ring aromatics are generally quite small it is preferred to utilize times ranging up to about one hour. Mixing times in the range of about 45 minutes have, in general, been found to be completely satisfactory with commercially available agitators.

Following the mixing period, the mixture of wax and dimethyl formamide is allowed to stand without agitation in order that it will separate into two phases, one phase, generally the upper layer, being rich in hydrocarbon wax but substantially free of condensed 4- and S-ring aromatics and the other phase, the lower layer, being rich in solvent containing the condensed 4- and 5-ring aromatic hydrocarbons. This settling or Stratification time, while not critical, should be sufiicient to permit substantially complete phase separation to occur. In general, this time may range from 5 to 30 minutes, however, 15 minutes has been found to be completely satisfactory in most instances. It is to be noted that agitators which are designed to produce colloidal dispersions should not be utilized since such type of agitation would prevent the desired and necesary phase separation.

After the mixture has been allowed to settle and the phases separated into two layers, the phases are separated from each other by conventional decantation methods. The small quantity of dimethyl formarnide solvent contained in the hydrocarbon wax fraction is removed by 4 thereafter the solvent is separated by filtration from the crystallized wax and distilled to recover it for reuse, leaving as a residue the condensed 4- and 5-ring aromatics which may be discarded.

The following examples are provided for the purpose of demonstrating the utility of the process of the instant invention as well as illustrating certain specific embodiments and critical features of the invention. These examples, however, should not be construed as limiting the invention to the exact process conditions set forth therein.

EXAMPLE I One part of chrysene, a condensed 4-ring aromatic hydrocarbon, per million parts of wax by weight was added to a sample of a microcrystalline wax. This sample of microcrystalline wax had been found to contain only 3 parts of pyrene and 4 parts of substituted pyrenes per billion parts by weight of Wax as the only naturallyoccurring hydrocarbons of the condensed 4- and S-ring aromatic hydrocarbons.

This microcrystalline wax had been produced by com ventional phenol and methyl ethyl ketone solvent extraction of a deasphalted heavy petroleum distillate bottoms fraction to give a finished wax having a melting point of approximately F., a color of approximately to 1 as measured by AST-M Method D-155, a kinematic viscosity of 14.48 centistokes at 210 R, an oil content of 0.88 percent, and a penetration at 77 F. of 12 as measured b-y ASTM Method D-132l.

The microcrystalline wax containing the one part per million by weight of added chrysene was separated into several portions in order to determine the percent of chrysene that could be extracted with dimethyl formamide at various temperatures and with various solventto-wax ratios. In each experiment the solvent and wax were mixed at the mixing temperature for 45 minutes, then allowed to settle for 15 minutes while maintaining the same temperature used during mixing and thereafter the phases were separated by decantation at the same temperature.

The conditions employed and the results obtained are set forth in Table I. The weight percentof chrysene extracted and recovered based on the amount added originally was determined by analyzingg the solvent phase by means of chromatographic separation of the chrysene and ultraviolet spectroscopy.

Table l Extraction Temperature (Temperature of Mixing, Settling, and Separation) Solvent to Wax Ratio (grams dimethyl tormamide per gram of wax) F. 230 F. 280 F.

Experiment N o. 1 (wt. percent recovered) recovered) recovered) 1st Extraction, 2 62 60 43 2nd Extraction, 0.4 3 2 4 Experiment No. 2 (wt. percent Experiment N0. 3 (Wt. percent Experiment No. 5 (wt. percent recovered) Experiment Experiment No. 8 (wt. No. 9 (wt. percent percent recovered) recovered) Experiment Experiment No. 10 (wt. No. 11 (wt. percent percent recovered) recovered) Experiment No. 4 (wt. percent recovered) Experiment No. 6 (wt. percent recovered) 1st Extraction, 0.63 mid Extraction, 0.4

Experiment N o. 7 (wt. percent recovered) 1st Extraction, 0.20 5 2nd Extraction, 0.40 46 Experiment No. 12 (wt. percent recovered) Only one Extraction, 3.33

1 Average of three duplicate experiments.

[It will be seen from these experimental results that the extraction temperature should range from about 5 F. to about 60 F. above the melting point of the wax.

The data also show that the solvent-to-wax weight ratio should be at least 0.5 (compare the 1st extraction of Experiment No. 7 with the 1st extraction of Experiment No. 4, for example). Moreover, it is apparent that two successive extractions of approximately equal ratios, although both may be relatively low (Experiment 4 or 5) give a greater total recovery than one large ratio extraction followed by a smaller ratio extraction (Experiment 1 or 2).

EXAMPLE II Two different condensed 4-ring aromatic hydrocarbons and two diiferent condensed 5-ring aromatic hydrocarbons were added to each of four diiferent portions of the same microcrystalline wax utilized in Example I in amounts ranging from 5 parts per billion by weight in one experiment to 40 parts per billion by weight in the last experiment of the group. In each experiment the wax was extracted with three successive extractions utilizing a solvent-to-wax ratio of 0.5 grams of dimethyl formamide per gram of wax in each extraction. The extraction temperature in each instance was 200 F. The total recovery of each compound in each experiment is set forth in Table 11 below.

1 Corrected for amount determined as naturally-occurring in the wax.

It will be seen from these data that exceedingly high recoveries of the various types of condensed ring aromatics can be obtained at extremely low concentration levels of the condensed ring aromatics in the wax.

The solvent phase after each extraction was cooled to 80 F. and the amount of Wax that crystallized out at this temperature was determined by filtering the wax from the dimethyl formarnide solution. This amount of wax was found to be of the order of 1 percent or less of the total amount of wax that had been treated originally. The dimethyl formarnide filtrate was admixed with an amount of cyclohexane equal to approximately one-half the volume of the dimethyl formamide solution and with an amount of water equal to approximately twice the volume of the dimethyl formamide solution. The condensed 4- and S-ring aromatic hydrocarbons which were extracted from the wax and which remained in the dimethyl formamide solvent at 80 F. together with the small amounts of wax hydrocarbons which also remained in the dimethyl formamide solvent at 80 F., were thus transferred into the cyclohexane solvent. Two phases were formed, one the cyclohexane solution, the other the dimethyl formamide-water phase.

The cyclohexane solution phase was separated from the dimethyl formamide-water phase by decantation and the cyclohexane evaporated. A residue amounting to less than 0.1 percent by weight of the weight of the original quantity of wax treated by the extraction procedure was obtained. The residue after weighing was redissolved in a small quantity of cyclohexane and the condensed 4- and S-ring aromatic hydrocarbons contained therein were determined by chromatographic separation and ultraviolet 6 spectroscopy. Since less than about 1 percent of th weight of the wax is dissolved in the dimethyl formamide solvent at the extraction temperature and since most of this can be recovered by crystallization at approximately room temperature, it is clear that the extraction method of this invention is highly specific for the extraction of the condensed 4- and 5-ring aromatic hydrocarbons.

If desired, the wax which separates at F. may be combined with the wax which has been extracted in order that less than 0.1 perecnt by weight of the wax is lost.

EXAMPLE III A refined paraffin wax having a melting point of approximately F.-l37 F. and which had been found to contain only about 12 parts per billion by weight of pyrene as the only aromatic hydrocarbon of the condensed 4- and 5'-ring aromatic hydrocarbons was divided into three portions.

There were added to one portion five parts each of dibenz[a,h]-anthracene, benzo[a]pyrene, chrysene, and pyrene per billion parts by weight of wax. To the second portion of the wax were added 10 parts per billion of each of these compounds and to the third portion were added 20 parts per billion of each of these compounds. The wax fractions were extracted with three successive extractions of dimethyl formamide using a solvent-to-wax ratio of 0.5 gram of dimethyl formamide per gram of wax and an extraction temperature of 200 F. in each extraction. Recoveries obtained are set forth in Table III.

Table III Amount of Each Aromatic Added in Parts Per Billion of Wax Experiment No. 17, 5 p.p.b. (wt. percent recovered) Experiment No. 18, 10 p.p.b. (Wt. percent recovered) Experiment No. 19, 20 p.p.b. (Wt. percent recovered) Dibenz [:1, h] anthracene 94 Benzo [a] pyrene 50 (approx) Ghrysene 81 Pyrene 1 48 Corrected for amount determined as naturally-occurring in the wax EXAMPLE IV A microcrystalline wax similar to that in Examples I and II but from a different source was extracted with three successive extractions of dimethyl iormamide utilizing a solvent-to-wax ratio of 0.5 gram dimethyl formamide per gram of microcrystalline wax. An extraction temperature of 200 F. was utilized and upon analysis it was found that 1.8 parts per million of chrysenes, 1.6 parts per million of benzanthracenes, 0.5 part per million of pyrenes, and 0.4 part per million of benzfluorenes had been extracted from the wax, thus demonstrating that when condensed 4- and S-ring aromatic hydrocarbons are naturally-occurring in a wax they can be extracted by the method of this invention. It will be noted that in each of these analyses the low molecular weight alkyl derivatives of the parent compound were determined and reported with the parent compound.

The same chromatographic separation and ultraviolet spectroscopy techniques were employed for the analyses in each of the foregoing Examples I to IV inclusive. The dimethyl formamide solvent phase after separation from the hydrocarbon phase was treated as described in Example -II, that is, the condensed 4- and S-ring aromatic hydrocarbons, together with the small amounts of other solids, were transferred into a cyclohexane solvent for analysis. The quantity of cyclohexane employed for redissolving the residue obtained when the first cyclohexane solvent was evaporated as described in Example 11 was adjusted such that an approximately 2 weight percent solution of solids in cyclohexane was obtained. This concentration was not critical but was found convenient for analysis.

A 30-inch chromatographic adsorbent column having an internal diameter of 10 millimeters and consisting of six equal separable sections was packed with a mixture of commercial powdered cellulose and powdered diatomaceous earth filter aid (Celite 545, a highly porous filter aid material) in the ratio of 2 parts by weight of cellulose to 1 part by weight of the diatomaceous-earth. Fifty milliliters of dimethyl formarnide were percolated over the packed column and a current of air under a pressure of pounds per square inch was passed through the column for 16 hours, leaving the column slightly wetted with the dimethyl formamide. A S-milliliter portion of the 2 percent cyclohexane solution of the extracted hydrocarbons was allowed to percolate through the adsorption column and this solution was followed by 50 milliliters of isooctane. The column was then broken into its separable sections and the hydrocarbons contained in the adsorbent in each section were separately eluted from the adsorbent by means of ethanol using approximately 100 milliliters per section. Each ethanol solution was qualitatively analyzed by ultraviolet spectroscopy in order to determine which sections contained the con densed 4- and S-ring aromatic hydrocarbons. v

In general, the condensed 4- and 5-ring aromatic hydrocarbons were found in the uppermost sections of the column. Each 100 milliliters of ethanol solution which contained the condensed 4- and S-ring aromatic hydrocarbons were admixed with 100 milliliters of cyclohexane and the admixture warmed gently to approximately 100 F. to obtain miscibility. After miscibility had been obtained, 500 milliliters of water were added to the solution, thereby producing an aqueous ethanol phase and a cyclohexane phase containing the hydrocarbons. The phases were separated by decantation and each cyclohexane phase after being evaporated to a 5 milliliter volume was percolated through a separate adsorption tube of the same type as described above except that in this percolation the cellulose-diatomaceous earth adsorbent had been wetted with a mixture of 25 milliliters of dimethyl formamide and 25 milliliters of ethanol. The excess dimethyl formamide-ethanol solution was removed with a current of air at 5 pounds per square inch for 16 hours, leaving the adsorbent only slightly wetted.

After each of the cyclohexane solutions had been percolated through its adsorbent, as has been described, a 30-milliliter portion of isooctane which had been saturated with dimethyl formamide at room temperature was percolated through each column. Each column was then broken into its sections and each section eluted with 100 milliliters of ethanol. Each ethanol solution was analyzed in the ultraviolet spectrometer to determine qualitatively the hydrocarbons contained therein. Thereafter, each ethanol solution was treated with cyclohexane and water as has been described in order to transfer the hydrocarbons into a cyclohexane solution, which solutions were finally analyzed in the ultraviolet spectrometer quantitatively for the condensed 4- and S-ring aromatics.

I claim:

1. A process for selectively extracting condensed 4- and 5-ring aromatic hydrocarbons from a hydrocarbon wax fraction containing said aromatic hydrocarbons which comprises mixing said hydrocarbon wax fraction with a dimethyl formamide solvent at a temperature ranging from about 5 F. to about 60 F. above the melting point of said hydrocarbon wax fraction, discontinuing the mixing of the wax and solvent to allow the mixture to separate into two phases, one rich in hydrocarbon wax and one rich in solvent containing the extracted condensed 4- and S-ring aromatic hydrocarbons, separating the phases and removing solvent from the hydrocarbon wax phase.

2. The process according to claim 1 in which the steps of mixing the hydrocarbon wax phase with dimethyl formamide, discontinuing the mixing and separating the wax and solvent phases are repeated at least once.

3. The process according to claim 1 in which the hydrocarbon wax fraction is a petroleum microcrystalline wax.

4. The process according to claim 1 in which the hydrocarbon wax fraction is a petroleum paraflin wax.

5. The process according to claim 2 in which the hy drocarbon wax fraction is a petroleum microcrystalline wax.

6. The process according to claim 2 in which the hydrocarbon wax fraction is a petroleum paraflin wax.

7. A process for selectively extracting condensed 4- and S-ring aromatic hydrocarbons from a hydrocarbon wax fraction containing said aromatic hydrocarbons which comprises mixing said hydrocarbon wax fraction with a dimethyl formamide solvent at a temperature ranging from about 5 F. to about 60 F. above the melting point of said hydrocarbon wax fraction with a solvent-to-wax weight ratio of from 0.511 to 5.0:1, discontinuing the mixing of the wax and solvent to allow the mixture to separate into two phases, one rich in hydrocarbon wax and one rich in solvent containing the extracted condensed 4- and S-ring aromatic hydrocarbons, separating the phases and removing solvent from the hydrocarbon wax phase.

8. The process according to claim 7 in which the steps of mixing the hydrocarbon wax phase with dimethyl formamide, discontinuing the mixing and separating the wax and solvent phases are repeated at least once.

9. The process according to claim 7 in which the hydrocarbon wax fraction is a petroleum microcrystalline wax.

10. The process according to claim 7 in which the hydrocarbon wax fraction is a petroleum paraffin wax.

11. The process according to claim 8 in which the hydrocarbon wax fraction is a petroleum microcrystalline wax.

12. The process according to claim 8 in which the hydrocarbon wax fraction is a petroleum parafiin wax.

References Cited in the file of this patent 30, No. 7, July 1951 (pp. 97-100).

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,058905 October 16, 1962 Thomas A. Washall It is hereby certified that error appears in the above numbered petent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 55, for "sych" read such column 2, line 24, after "p'henanthrene", first occurrence, insert a closing parenthesis; column 4, line 43, for "analyzingg" read analyzing Signed and sealed this 5th day of March 1963.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD Attesting Officer Commissioner of Patents 

1. A PROCESS FOR SELECTIVELY EXTRACTING CONDENSED 4- AND 5-RING AROMATIC HYDROCARBONS FROM A HYDROCARBON WAX FRACTION CONTAINING SAID AROMATIC HYDROCABONS WHICH COMPRISES MIXING SAID HYDROCARBON WAX FRACTION WITH A DIMETHYL FROMAMIDE SOLVENT AT A TEMPERATURE RANGING FROM ABOUT 5*F. TO ABOUT 60*F. ABOVE THE MELTING POINT OF SAID HYDROCARBON WAX FRACTION, DISCONTINUING THE MIXING OF THE WAX AND SOLVENT TO ALLOW THE MIXTURE TO SEPARATE INTO TWO PHASES, ONE RICH IN HYDROCARBONS WAX AND ONE RICH IN SOLVENT CONTAINING THE EXTRACTED CONDENSED 4AND 5-RING AROMATIC HYDROCARBONS, SEPARATING THE PHASES AND REMOVING SOLVENT FROM THE HYDROCARBON WAX PHASE. 